The present invention relates to a pneumatic tire and an innerliner containing chlorinated polyethylene elastomer and method for manufacturing a pneumatic tire.
The inner surface of pneumatic tires generally include an elastomeric composition designed to prevent or retard air and moisture permeation and maintain tire pressure. This elastomeric composition is often referred to as the innerliner. Butyl rubber and halobutyl rubber are commonly used for forming pneumatic tire innerliners because they are relatively impermeable to air and moisture and exhibit other desirable physical properties; such as, flex fatigue resistance and age durability. Chlorobutyl rubber is probably the most commonly used innerliner material.
Butyl rubber and halobutyl rubber are expensive. As a result, it is desirable to provide a less expensive material for pneumatic tire innerliners while maintaining the desirable properties of air and moisture impermeability, flex fatigue resistance and aged durability, and without adversely affecting the performance of the tire. Alternatives to butyl rubber have been proposed. For example, U.S. Pat. No. 5,178,702 to Frerking, Jr. et al describes a multi-layered innerliner prepared from at least two barrier layers of sulfur-cured rubber composition containing acrylonitrile/diene copolymer and a nonbarrier layer of sulfur-cured rubber therebetween. U.S. Pat. No. 5,040,583 to Lin et al describes an innerliner having non-elastomeric barrier layers of vinylidene chloride polymer or ethylene-vinyl alcohol copolymer sandwiched between two layers of elastomeric material.
Chlorinated polyethylene has been proposed for use as a barrier layer for a pneumatic tire innerliner. According to WO 92/20538 which was published on Nov. 26, 1992, a film prepared from chlorinated polyethylene containing 35 to 50 percent by weight chlorine, a derivative of 2,5-dimercapto-l-3,4 thiazole as a curative, an accelerator, an acid acceptor and optionally carbon black can provide an innerliner which is lighter than butyl or halobutyl rubbers without losing air impermeability, heat resistance and mechanical properties. It is recognized, however, that chlorinated polyethylene exhibits poor adhesion to a tire. The WO 92/20538 publication describes adhering the chlorinated polyethylene to a tire by using an adhesive resin based on styrenic block copolymer, ethylene-vinyl acetate or a blend of ethylene-vinyl acetate and styrenic block copolymer.
The invention is directed toward pneumatic tires having an innerliner which includes a multilayer structure. The multilayer structure includes a barrier layer for providing barrier properties and an adhesive layer for adhering the barrier layer to the tire carcass. In a preferred embodiment, the barrier layer includes a blend of high chlorine content chlorinated polyethylene elastomer and low chlorine content chlorinated polyethylene elastomer. The high chlorine content chlorinated polyethylene elastomer preferably has a chlorine content of between about 35 percent to about 45 percent and more preferably between about 38 percent to about 43 percent. The low chlorine content chlorinated polyethylene polymer preferably has a chlorine content of between about 25 percent to about 35 percent and more preferably between about 28 percent to about 32 percent. The adhesive layer includes a polymer composition for adhering the barrier layer to the carcass. The innerliner provides an oxygen permeability of less than 250 cc-mil/100 in2-atm-day and preferably less than about 200 cc-mil/100 in2-atm-day and good cold flexibility at xe2x88x9240xc2x0 C.
In a preferred embodiment of the invention, the adhesive layer can include a nitrile rubber composition having an acrylonitrile content of between about 16 percent and about 27 percent. Alternatively, the adhesive layer can include an ultra high molecular weight polyethylene elastomer. It is desired that the adhesive layer can provide a peel strength of at least 5 lb/in for adhering the barrier layer to the carcass.
The subject invention specifically discloses a pneumatic tire comprising a carcass and an innerliner, said innerliner comprising a multilayer structure including a barrier layer and an adhesive layer, the barrier layer comprising a blend of high chlorine content chlorinated polyethylene elastomer and low chlorine content chlorinated polyethylene elastomer, the high chlorine content chlorinated polyethylene elastomer having a chlorine content of between about 35 percent to about 45 percent and the low chlorine content chlorinated polyethylene polymer having a chlorine content of between about 25 percent to about 35 percent, wherein the high chlorine content polyethylene has a chlorine content which is at least 5 percentage points higher that the chlorine content of the low chlorine content polyethylene; the adhesive layer comprising a polymer composition for adhering the barrier layer to said rubber carcass; and wherein the innerliner provides an oxygen permeability of less than 250 cc-mil/100 in2-atm-day at 65xc2x0 C. and a cold flexibility at xe2x88x9240xc2x0 C.
The present invention also discloses an innerliner for use in a pneumatic tire comprising: a multilayer structure including a barrier layer and an adhesive layer, the barrier layer comprising a blend of high chlorine content chlorinated polyethylene elastomer and low chlorine content chlorinated polyethylene elastomer, the high chlorine content chlorinated polyethylene elastomer having a chlorine content of between about 35 percent to about 50 percent and the low chlorine content chlorinated polyethylene polymer having a chlorine content of between about 20 percent to about 38 percent; and the adhesive layer includes a rubber material for adhering the barrier layer to another surface.